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HotScience last updated: 19 February 2003
Added 22 October 2003:
Gill, B. J. 2003. Osteometry and systematics of the extinct New Zealand ravens (Aves: Corvidae: Corvus). Journal of Systematic Palaeontology 1: 43-58.
Measurements of Holocene raven bones show that birds from the Chatham Islands were significantly larger than those from the South Island, which were in turn larger than North Island birds. Three taxa are recognised: the Chatham Islands raven Corvus moriorum, the North Island raven C. antipodum antipodum, and the South Island raven C. a. pycrafti. New Zealand ravens were the largest crows in the Australasian region, and the Chatham Islands raven was probably the world's fourth- or fifth-largest passerine. New Zealand ravens were strong fliers with no reduction in flying ability compared to weak-flying New Zealand birds like the kokako. /p>
Husheer, S.W.; Coomes, D.A.; Robertson, A.W. 2003. Long-term influences of introduced deer on the composition and structure of New Zealand Nothofagus forests. Forest Ecology and Management 181: 99-117.
This study uses data from ninety-two 20 m x 20 m permanent plots and three pairs of exclosure plots monitored for two decades in Kaimanawa Forest Park. Mountain beech forest composition has shifted towards browse-resistant shrub species, while intense deer browsing may have led to the development of turf-forming communities. In red and silver beech forests there was an increase in the stem densities of small trees that are unpalatable to deer. This is the first time in New Zealand that observed deer impacts in the understorey have been clearly related to changes in overstorey composition on a landscape scale.
Added 3 July 2003:
Gillman, L.N. & Ogden, J. 2003. Seedling mortality and damage due to non-trophic animal interactions in a northern New Zealand forest. Austral Ecology 28: 48-52.
The influence of mammal browse on indigenous tree seedlings has been extensively studied in New Zealand. However, the importance of non-trophic damage by animals (such as biting and uprooting without consump-tion) has received little attention. In this study, seedling mortality due to non-trophic animal damage (37.5% of all mortalities) was greater than for any other cause. Most of the seedlings non-trophically damaged were bitten off close to the ground and left uneaten (73%), and the remainder were uprooted. Evidence is presented that suggests that the non-trophic damage to these seedlings was caused by rabbits.
Holzapfel, S. 2001. Studies of the New Zealand root- parasite Dactylanthus taylorii (Balanophoraceae). Englera 22: 1–176.
New research on flower anatomy, seed development, germination, vegetative reproduction, infection of host trees and genetic diversity of the endemic root-parasite Dactylanthus taylorii. A number of misinterpretations and generalisations in the literature about the family and the species itself are clarified. The anatomy of the female flower is described at various stages of development and the embryo of D. taylorii is described for the first time. Seeds are able to germinate without the presence of a host tree. RAPDs show genetic distinctness of even neighbour-ing populations and did not support the occurrence of monoecy in D. taylorii. Includes illustrations.
Holzapfel, S., Faville, M. & Gemmill, C.E.C. 2002. Genetic variation of the endangered holoparasite Dactylanthus taylorii (Balanophoraceae) in New Zealand. Journal of Biogeography 29: 663–676.
Genetic variation among seventeen populations from the entire known range of the endemic root parasite Dactylanthus taylorii is studied using RAPDs. Markers show that all sampled populations are unique and can be grouped into two main clusters, corresponding to an eastern and western distribution separated by the Taupo Volcanic Zone. Observed genetic variation is predomi-nantly among as opposed to within populations and is not correlated with geographical distance below the regional scale. Results indicate long isolation and restricted gene flow among populations and are interpreted mainly as characteristics of the species. The role of vegetation disturbance through volcanism is discussed.
Keedwell, R.J., & Sanders, M.D. 2002. Nest monitoring and predator visitation at nests of banded dot-terels. The Condor 104: 899–902.
We used video cameras to monitor nests of the banded dotterel (Charadrius bicinctus), to test whether conven-tional nest monitoring increased the chances of nests being visited by predators. We compared the predator visitation rates to 22 video-monitored nests, which were approached on foot daily to simulate conventional monitoring, with that of 17 nests that were monitored using video cameras only. Predator visitation rates did not differ, nor was there any evidence that predators used human scent trails to locate nests. This study provides evidence that monitoring banded dotterel nests by regularly checking them does not influence their risk of predation.
Keedwell, R.J., Sanders, M.D., Alley, M., & Twentyman, C. 2002. Causes of mortality of black- fronted terns (Sterna albostriata) in the Ohau River, South Island, New Zealand. Pacific Conservation Biology 8: 170–176.
The carcasses of 148 Black-fronted terns Sterna albostriata found during the 1998–2000 breeding seasons on the Ohau River were examined to determine causes of mortality. Predation was the primary cause of mortality of adults, juveniles and chicks, resulting in 47% of all deaths. Feral cats Felis catus, Norway rats Rattus norvegicus and, to a lesser extent, stoats Mustela erminea were the main predators responsible. The prey remains left by the different predator species are described. Predators are potentially the main cause of population decline in black- fronted terns and predator control during the breeding season should be trialled.
Leathwick, J. R., & Whitehead, D. 2001. Soil and atmospheric water deficits and the distributions of New Zealand’s indigenous tree species. Functional Ecology 15: 233–242.
This paper explores relationships between native tree species distributions and climate, with a particular focus on water relations. Results highlight the likely role of föhn winds that produce very high air saturation deficits in explaining the low abundance of many species east of New Zealand’s main mountain ranges. They also suggest that reduced rainfall in dry years is more important in affecting species distributions than long-term average rainfall.
Leathwick, J. R.; & Austin, M. P. 2001. Competitive interactions between tree species in New Zealand’s old-growth indigenous forests. Ecology 82: 2560– 2573.
This paper presents results of an analysis that uses the Nothofagus disjunctions as a natural removal ‘experiment’ to quantify the effects of competition from these patchily distributed species on other widespread tree species. Relationships between species distributions and environment are first analysed using multiple regressions, and then the magnitude of competition effects are assessed by adding statistical terms describing Nothofagus abundance. Results indicate that many species are substantially reduced in abundance in the presence of Nothofagus. In addition, both the shape of species responses to annual temperature and their optima vary as Nothofagus abundance increases.
Leathwick, J. R. 2002. Intra-generic competition among Nothofagus in New Zealand’s primary indigenous forests. Biodiversity and Conservation 11: 2177–2187.
This paper extends the analysis described in Leathwick & Austin (2001) by considering competitive interactions within the genus Nothofagus. Species responses to environment were first assessed using multiple regressions, to which were added terms to assess changes in both overall abundance and species responses to annual temperature with increasing numbers of congeners. Results indicate that variation in abundance along the annual temperature gradient is strongly influenced by the competitive context provided by the remaining congeners. Red and silver beech also appear to behave in a mutualistic fashion, reaching greater abundance when growing together than when growing with other species.
McAlpine, K. G.; Drake, D. R. 2003. The effects of small-scale environmental heterogeneity on seed germination in experimental treefall gaps in New Zealand. Plant Ecology 165: 207–215.
Seed germination of native and exotic woody species was studied in treefall gaps to assess how environmental heterogeneity affects regeneration from seed. Gaps were created in a relictual pine plantation destined for restoration to native forest. Seeds of Alectryon excelsus,Macropiper excelsum, Fuchsia excorticata, Cytisus scoparius and Berberis darwinii were sown in sites differing in exposure, with and without 3 cm of pine litter. Effects of litter and degree of exposure on germination varied with species. Results suggest that microenvironmental heterogeneity can be an important influence on the species composition of regenerating vegetation within and around treefall gaps.
Pierce R.J.; & Westbrooke I.M. 2003. Call count responses of North Island brown kiwi to different levels of predator control in Northland, New Zealand. Biological Conservation 109: 175–180.
This paper evaluates whether there are any trends in call counts that relate to predator control and advocacy in and around 23 kiwi listening stations monitored in Northland since 1995. Both predator and advocacy effort were rated on a 0–3 scale at each listening station, and kiwi calling rates analysed in a generalised linear model. An ANOVA indicated a positive response of call counts to predator control. There was a weaker relationship with advocacy, but because predator control and advocacy are correlated, it was not possible to separate their effects. Overall, the analysis suggested that this kind of management is benefiting kiwi in Northland.
Added 19 February 2003:
Gillman, L.N., Wright, S.D., & Ogden, J. 2002. Use of artificial seedlings to estimate damage of forest seedlings due to litterfall and animals. Journal of Vegetation Science 13: 635–640.
Artificial seedlings are often used to estimate seedling mortality due to non-trophic micro-disturbance such as litterfall and up-rooting. This study evaluated the use of artificial seedlings in five New Zealand forests. It was concluded that artificial seedlings could not be used to estimate mortality, and were vulnerable to a novelty response by animals. The value, however, of artificial seedlings is that they provide a good measure of litterfall disturbance potential that is independent of natural seedling clumping within litterfall safe-sites, and independent of species specific resistance to damage. Thus, they can be used to compare litterfall damage risk among microsites and forests.
Joy, M. K.; Death, R. G. 2002. Predictive modelling of freshwater fish as a biomonitoring tool in New Zealand. Freshwater Biology 47: 2261–2275.
The paper describes the first application of a regional predictive model using freshwater fish for bioassessment in New Zealand. Fish assemblages were surveyed at 200 reference sites in the Manawatu–Wanganui region. These “reference sites” represent the best available conditions covering the full range of stream types in the region. They were used to predict the fish assemblages to be expected in the absence of impacts using multivariate analysis based on environmental variables. Test site fish assemblages were compared with expected assemblages using weighted probabilities from reference sites using an observed over ex-pected (O/E) ratio.
Kelly, D.; Sork, V. L. 2002. Mast seeding in perennial plants: why, how, where? Annual Review of Ecology and Systematics 33:427–447.
This paper firstly reviews the possible causes of mast seeding. It tests the null hypothesis (variable weather causes variable seed-ing) and finds few convincing cases, then reviews the main selective hypotheses (predator satiation, enhanced pollination, animal dispersal). The second part analyses 570 masting datasets worldwide. Interestingly, 17 of the 26 datasets >24 yrs were from New Zealand. The analysis shows that masting is more pro-nounced in mid latitudes, in the southern hemisphere, in wind pollinated and abiotically dispersed plants, and in plants dis-persed by seed predators. Masting is predicted to be rare in the tropics, but more pronounced at unproductive sites.
O’Donnell, C. F. J. 2000. Cryptic local populations in a temperate rainforest bat Chalinolobus tuberculatus in New Zealand. Animal Conservation 3: 287–297.
Long-tailed bats form long term non-random associations among individuals. Three distinct social groups (72–132 bats) were cryptic because foraging ranges overlapped, bats belonging to each group spread over many roosts each day, and these roost sites changed from day to day. Bats moved infrequently between groups (1.6% of recaptures), potentially linking the local population assemblages. Population structure did not conform to traditional metapopulation models because groups occurred in homogeneous habitat extending over a large area. Conservation of bat populations should entail protecting representative sub-groups, but development of models for predicting minimum number of effective local populations is still required.
O’Donnell, C. F. J. 2000. Conservation status and causes of decline of the threatened New Zealand Long-tailed Bat Chalinolobus tuberculatus (Chiroptera: Vespertilionidae). Mammal Review 30: 89–106.
Historical anecdotes and monitoring since 1990, indicate that long-tailed bats are now rare or absent at many sites where formerly they were common. Assertions in the literature that they are “common” and that the conservation status is “secure” are incorrect and the species should be classed as “Vulnerable”. Possible causes of decline include clearance and logging of lowland forests, predation by introduced mammals and owls, competition for roost sites by introduced mammals, birds and wasps, and human interference and disturbance at roosting sites.
O’Donnell, C. F. J. 2001. Home range and use of space by Chalinolobus tuberculatus, a temperate rainforest bat from New Zealand. Journal of Zoology (London) 253: 253–264.
Home range sizes in long-tailed bats were among the largest published for Microchiroptera. These bats were highly mobile. One colony ranged over 100 km² and range size varied among age and sex classes (medians = 237–2,006 ha; max 5629 ha). A prediction that these bats have large ranges to minimise overlap between foraging bats, reflecting scarcity of food, requires testing. Large range size and the degree of individual spacing implies that conservation areas designed for bats should be large.
O’Donnell, C. F. J. 2002. Influence of sex and reproductive status on nocturnal activity and night roost-ing by the New Zealand long-tailed bat Chalinolobus tuberculatus. Journal of Mammalogy 83: 794–803.
This paper tests the hypothesis that reproductive long-tailed bats should forage for longer than other classes. Length of active periods did not differ among reproductive females, non-repro-ductive females, and adult males. Reproductive females were active for significantly longer during lactation than during preg-nancy but not post-lactation. I predict few differences between reproductive classes because: energy demands are high through-out the reproductive cycle; females have different mechanisms, such as increasing foraging efficiency, using torpor, and select-ing thermally beneficial roosts, for balancing high energy re-quirements; and energy demands limit all classes in the cold temperate climate when food is in short supply.
O’Donnell, C. F. J. 2002. Timing of breeding, produc-tivity and survival of long-tailed bats Chalinolobus tuberculatus (Chiroptera: Vespertilionidae) in cold- temperate rainforest in New Zealand. Journal of Zoology (London) 257: 311–323.
This paper reports on breeding of long-tailed bats for the first time. Most births occurred over 10 days in mid-December. Young began flying at 5–6 weeks. Lactation coincided with highest temperatures and peak abundance of insects. Annual survival of juveniles varied from 0.26–0.88. The short, highly synchronous breeding season, birth of single young, early mat-ing, and late age of sexual maturity compared to similar-sized bats, may be related to low food availability and unpredictable cold-temperate weather conditions. Poor productivity in 1996 coincided with an irruption of stoats, implying that predation may cause population crashes.
Sedgeley, J. A. 2001. Quality of cavity micro-climate as a factor influencing maternity roost selection by a tree-dwelling bat, Chalinolobus tuberculatus, in New Zealand. Journal of Applied Ecology 38: 425–438.
Building on recent work that showed that long-tailed bats were highly selective of trees and cavities for roosting (Biological Conservation 88:261–276; J. Zoology London 249:437–446), this paper shows that these bats selected cavities on the basis of their thermoregulatory quality. Cavities used conveyed significant thermoregulatory advantages to roost occupants, especially reproductive females during the day and non-volant young, which were left alone for most of the night. Bat roosts had stable microclimates, displaying small ranges in temperature and hu-midity compared with external ambient conditions and available cavities that were not used by bats.
Sedgeley, J. A. 2001. Winter activity in the tree- roosting lesser short-tailed bat, Mystacina tuberculata, in cold-temperate climate in New Zealand. Acta Chiropterologica 3: 179–195
Unusually high levels of activity compared to other small bats in temperate forests were detected in the short-tailed bats during winter on Codfish Island. Radio-tagged bats flew on >50% of nights including those where minimum temperatures were 0 °C. Large levels of activity were recorded at roosts (max. = 1443 bats). Periods of activity were associated with feeding, social displays and changing roosts. Winter activity may not be as energetically expensive for short-tailed bats as other cold-temperate bat species. Their ability to forage on terrestrial invertebrates and to select different roost sites, allow them to be active more frequently and for longer.
Wardle, D. A.; Barker, G. M.; Yeates, G. W.; Bonner, K. I.; Ghani, A. 2001. Introduced browsing mammals in natural New Zealand forests: aboveground and belowground consequences. Ecological Monographs 71: 587–614.
The effects of browsing mammals (deer and goats) on plant and soil microbial and invertebrate communities was assessed for each of 30 long term exclosure plots in forests located throughout New Zealand. While browse layer vegetation density and diver-sity was consistently adversely affected by herbivores, the soil biota showed varied responses, and only invertebrates with larger body sizes were consistently adversely affected. There were also several instances in which browsers affected decomposer diversity, key soil processes and soil carbon and nitrogen sequestration. Frequently below-ground effects of these mammals were more severe than we would predict based on the response of vegetation.
Wardle, D. A.; Bonner, K. I.; Barker, G. M. 2002. Linkages between plant litter decomposition, litter quality, and vegetation responses to herbivores. Functional Ecology 16: 585–595.
To predict possible effects of deer and goats on the decomposer subsystem, litter from several understorey plant species were collected from 28 forested locations throughout New Zealand. At each location exclosure plots were used to determine effects of browsing mammals on each plant species. Litters from those species which were reduced by browsers decomposed more rapidly, and had lower concentrations of phenolics, tannins, lignin and fibre than those promoted by browsers; litter N and P concentrations did not differ between these two types of plants. This suggests that browsing results in understorey domination by plant species that impair decomposer processes.
Added 4 November 2002:
Lord, A., Waas, J.R., Innes, J., & Whittingham, M.J. 2001. Effects of human approaches to nests of northern NZ dotterels. Biological Conservation 98: 233-240.
People and dogs disturbing nesting NZ dotterels potentially decrease their nesting success. Dotterels flushed at greater distances and for longer times when there was a dog with the person, while responses to people walking and running did not differ. The results suggest that disruption would be greatly reduced if dogs were banned within 100m of nesting dotterels. Human access should be prevented within a 50 m radius on busy beaches, and 70 m on remote beaches.
Moles, A. T.; Hodson, D. W.; Webb, C. J. 2000. Do seed size and shape predict persistence in soil in New Zealand? Oikos 89: 541-545.
European species with small, rounded seeds have persistent seed banks, but species with larger, elongate or flattened seeds usually lack persistence. This may be because small, rounded seeds are easily incorporated into the soil, and therefore have less exposure to seed predators. We tested whether seed size and shape could predict persistence in soil in 47 species native to New Zealand forests. Species with persistent seeds had significantly smaller seeds than transient-seeded species. However, some species did have large and/or elongate persistent seeds. Perhaps these species can persist because of the low levels of seed predation observed in New Zealand.
Toft, R. J.; Harris, R. J.; Williams, P. A. 2001. Impacts of the weed Tradescantia fluminensis on insect communities in fragmented forests in New Zealand. Biological Conservation 102: 31Ð46.
The impact of Tradescantia on insect communities, as represented by Malaise-trapped beetles and fungus gnats (Diptera: Mycetophilidae s. l.), was studied at three lowland forest fragments in the southern North Island. The proportion of Tradescantia cover within study plots was a poor predictor of species richness for either beetles or fungus gnats, but there was evidence that particular taxa were affected. The richness of beetle and fungus gnat species was correlated with vascular plant richness. As Tradescantia is known to prevent regeneration of many native plants, we predict a corresponding decline in invertebrate diversity and fragment complementarity where the weed is established.
Young, J.R.; Kearvell, J.C. 2001. Distinguishing between sexes and species: bill size in orange-fronted and yellow-crowned parakeets, Cyanoramphus auriceps. Emu 101:137-143, 2001.
Controversy surrounds the taxonomic status of the Orange-fronted Parakeet (previously known as Cyanoramphus malherbi), officially a colour morph of the more common Yellow-crowned Parakeet C. auriceps. We analyse bill length and bill width measurements from 60 museum specimens of Orange-fronted Parakeet and 44 museum specimens of Yellow-crowned Parakeet. Male Orange-fronted Parakeets have shorter bills than male Yellow-crowned Parakeets Ñ the difference between sample means is 0.7Ð0.8 mm. Power calculations show that others have most likely not seen the difference as significant because of small sample sizes. Our analysis illustrates a useful statistical technique for identifying morphological differences between two species where both species are sexually dimorphic but the sex of each individual is uncertain.
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